3D hinge transport in acoustic higher-order topological insulators

Abstract

The discovery of topologically protected boundary states in topological insulators opens a new avenue toward exploring novel transport phenomena. The one-way feature of boundary states against disorders and impurities prospects great potential in applications of electronic and classical wave devices. Particularly, for the 3D higher-order topological insulators, it can host hinge states, which allow the energy to transport along the hinge channels. However, the hinge states haveonly been observed along a single hinge, and a natural question arises: whether the hinge states can exist simultaneously on all the three independent directions of one sample? Here we theoretically predict and experimentally observe the hinge states on three different directions of a higher-order topological phononic crystal, and demonstrate their robust one-way transport from hinge to hinge. Therefore, 3D topological hinge transport is successfully achieved. The novel sound transport may serve as the basis for acoustic devices of unconventional functions.

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• Reflection symmetric second-order topological insulators and superconductors
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• Higher-Order Weyl Semimetals
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• Higher-order topological phases in crystalline and non-crystalline systems: a review
• Realization of Surface-Obstructed Topological Insulators
• Dirac States in an Inclined Two-Dimensional Su-Schrieffer-Heeger Model
• Klein-bottle quadrupole insulators and Dirac semimetals
• Unified characterization for higher-order topological phase transitions
• Topological States in Two-Dimensional Su-Schrieffer-Heeger Models
• Unveiling Higher-Order Topology via Polarized Topological Charges
• Higher-order topology in twisted multilayer systems: a review
• Topological Corner States in Bilayer and Trilayer Systems with Vertically Stacked Topological Heterostructures
• Hybrid-Order Topological Phase And Transition in 1H Transition Metal Compounds
• Floquet topological phases with time-reversal and space inversion symmetries and dynamical detection of topological charges
• Nonlinearity-induced corner states in a kagome lattice
• Breakdown of the symmetry constraint in a Floquet topological insulator
• Topological Pseudospin Hall Effect and Multi-frequency Corner Modes in Kagome-based Lattices